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Troubleshooting - System continuously cycles power on/off

  • Homebuilt
  • Power
  • Systems
Last response: in Systems
April 29, 2012 5:41:42 PM

Hi! I'm troubleshooting a homebuilt desktop that's been in use for at least a year with no problems. Suddenly, as of a few weeks ago, I can't get it to post with everything connected. Most of the time when I press power, everything lights up and all of the fans rev, but after about 1 or 2 seconds, it dies and tries to restart. Once in a while it will get a bit further, but this doesn't seem to have to do with cold vs. hot, rather it's more sporadic.

First thing I did was check all of the connectors on the power supply using a voltage tester. Everything checked out, but I'm not sure if that rules out a bad PSU, since it may be under heavy load? (But, like I said, the PC has been used in this configuration for over a year)

I took everything out of the box in case of a short and breadboarded it. Just the PSU connected to the motherboard with the CPU and fan in gives me an expected series of long beeps (no memory).

With the memory added but no video card I get no beeps but the fans run and everything lights up like it should. No repeated power-offs like I mentioned.

Adding the video card (PCI-E with a six-pin connector. I think it's a geforce 8000 series?) I still have no problems. In fact, I get display with "No bootable device was found." which is encouraging!

Then, when I connect either the CD/DVD drive or the hard drive I get the same problem I mentioned above. Everything turns on, revs, and then shuts off, then automatically tries to start again.

Interestingly, up until I connect the HDD or the CD/DVD, I have to turn on the power supply and then jump the power pins on the mobo to get it to start. Once the HDD or CD/DVD is connected, though, as soon as I turn on the power supply, everything turns on.

I'm guessing this is a power issue, but I'm not quite sure. The other thing I've read around is that it may be thermal paste on the CPU, but it doesn't seem like it runs long enough to be an overheating issue... I don't want to put a ton of money into this system just guessing parts, because it's not a very high-end, expensive system in the first place. What would people here suggest I look at next?

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April 30, 2012 11:42:12 PM

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Any ideas?